william lajeunesse is in los angeles with more. william, all of a sudden these guys can, and women can do their own thing. >> that's right, brian. with alcohol, people know, three drinks, think twice about driving. but pot, it is different. where it is grown, how it is grown, how it is smoked, how much you have. those are all variables that determine if a person is impaired or committing a duid, driving under the influence of drugs. >> you want to know why i pulled you over? littering and smoke the reefer. >> driving while high. while illegal, research shows more drivers are teching up. yet studies like this one in europe showed too much marijuana affects coordination and judgment. >> one of the first and most important things is inability to divide one's attention. >> rick: marijuana advocates argue pot is far less debill date faithing than alcohol, yet a new study says those who drive within three hours of smoking pot are twice as likely to cause a crash. >> another one of the effects that we see with individuals who drive under